The apparatus relates to aftermarket (as well as OEM) trigger assemblies that are particularly adapted to be mounted in firearms. Specifically, in one form the apparatus is adapted to be retrofitted or initially installed to an AR-15 semiautomatic rifle.
After market triggers have been provided for rifles to replace factory trigger assemblies. Factory trigger assemblies are notoriously poor where a shooter's accuracy is compromised where the trigger has excessive over travel (where the trigger will travel excessive rearwardly after releasing a hammer) or have what is referred to as take up. Take up is an undesirable movement of the trigger prior to releasing the hammer.
In general, most shooters find it desirable when a trigger breaks like a “glass rod”. In some military applications the trigger pull is up to 12 lbs. It is desirable lighten this trigger pull for a more accurate placement of a shot without undesirably altering the rifles position when pulling the trigger.
One challenge with aftermarket triggers is providing a suitably adjustable trigger that requires very little end-user involvement to retrofit to their existing lower receiver of an AR-15. In general, certain prior art methods of providing an adjustable trigger required employing setscrews where the end surface of the screw applies a pressure upon the lower surface in the cavity region with the trigger assembly is housed. Of course the relationships between the laterally extending pins and the upper surface of this chamber region can vary between firearms where an adjustable assembly of setscrews must be provided. A challenge to providing this adjustability is the end-user or installer of the aftermarket trigger assembly must manually adjust the setscrews and use a proper thread locking compound to ensure the screws do not change. The problems are further compounded where certain lower receivers are made from nonmetallic materials and the setscrews can wear out holes and change the various relationships of the dimensions between the laterally extending pins and the engagement surfaces provided for the setscrews. This possibly could change the action of the trigger overtime and potentially present a hazardous condition where the trigger may accidentally misfire. Of course, the problem of having the installer who may not be familiar with the process presents an opportunity for disaster if a prior art aftermarket trigger is not adjusted properly. For example, the geometries and orientations of the sear engagement surfaces between the disconnector and the hammer could be improper whereby misfire would occur with a certain vector acceleration of the firearm.